1. Field of the Invention
The present invention relates to an image acquisition apparatus that acquires image signals associated with a plurality of images by carrying out image acquisition of the same subject multiple times and generates a combined image signal from the plurality of image signals.
2. Description of Related Art
In general, the dynamic range of various solid-state image-acquisition devices used for electronic cameras, such as CCD image sensors and CMOS-type image sensors, is small compared with the dynamic range of a subject. Thus, there is a problem in that overexposure occurs in high-luminance sections, and underexposure occurs in low-luminance sections. Accordingly, a method of generating an image having an expanded dynamic range by combining multiple image signals having different exposure levels into an image signal for one image has been proposed.
Japanese Unexamined Patent Application, Publication No. 2007-324770 discloses a method of acquiring an image with reduced noise by combining an image with short exposure time, high resolution, and a high level of noise and an image with long exposure time, low resolution, and a low level of noise.
Japanese Unexamined Patent Application, Publication No. 2002-112108 discloses a method of emphasizing the sharpness of image-acquisition signals, detecting the exposure ratio of image acquisition carried out multiple times, and combining the plurality of image-acquisition signals with emphasized sharpness depending on the exposure ratio.